Electrode for electrosurgical ablation of tissue

ABSTRACT

An electrosurgical probe is provided to vaporize, cut, coagulate or remove tissue from a body structure. A method of surgically treating a mammal includes providing a surgical instrument including a length of shaft and an active electrode having a curved current density edge with at least one convex surface; and ablating a tissue surface with said surgical instrument.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part under 35 U.S.C. 120 ofcopending U.S. Ser. No. 09/022,612, filed Feb. 12, 1998 which is acontinuation-in-part of Ser. No. 60/037.782, filed Feb. 12. 1997 both ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] The invention relates to surgical systems applying thermal energyto biological tissue to modify the characteristics of the tissue. Moreparticularly, the invention is directed to electrosurgical probesutilizing radiofrequency (RF) energy to cut, coagulate, ablate and/orvaporize the tissue during a medical procedure for treatment andtherapy.

[0003] Arthroscopic surgery is becoming increasingly popular, because itgenerally does less damage, is less invasive and is safer than openprocedures and produces less scarring in and around joints. This type ofsurgery further results in a faster healing response and a quickerreturn of the patient to full productivity while reducing costs of opensurgical procedures.

[0004] Nevertheless, arthroscopic surgery has its limitations. Thesurgeon must operate through a narrow tube, which is awkward. Only oneprobe can be used at a time. Often the viewing camera is positioned atan angle which is different from the surgeon's normal gaze. Thiscontrasts with “open surgery” where the surgeon has relative ease ofviewing the surgical site and can freely move both hands, even utilizingthe hands of colleagues.

[0005] In view of such difficulties of arthroscopic surgery, it isunderstandable that laser, microwave and radiofrequency (RF) probeswhich simultaneously cut and coagulate are preferred. However, currentprobes are poorly adapted to certain activities, such as cutting narrowtendons or ligaments. Current probes have convex, pointed and/or flattips. Other probes such as those utilizing laser energy delivery systemsoften provide pointed tips with curved configurations, with currentprobes, the surgeon has little control when pressing against a toughligament. Now as the surgeon cuts through one portion of the ligament,the probe slips out of position. The surgeon must reapproximate theprobe and cut again, an inefficient process. Unless the surgeon is ableto stop pressure at exactly the right time, the probe may slip and cutan adjacent structure. Because the surgeon must repeatedly reapproximateand cut the ligament, the surgeon has difficulty in cleanly ablating theligament or tendon. Thus, there are certain procedures that surgeonsstill prefer to perform in an open setting which is conventionallytermed an “open” procedure. Unfortunately, this often results in largescars, long convalescence, and even more irritation of an alreadyirritated joint.

[0006] What is needed is a probe that can simultaneously direct thetendon to the energy source (e.g., RF) and apply RF to cleanly andsmoothly ablate the tendon or ligament. The advantage is that someprocedures that have been considered too awkward or difficult to performby arthroscopy can now be performed more effectively using arthroscopicdevices.

[0007] Moreover, conventional and more complex surgical probes andlasers are less suitable for critical and precise shaping and sculptingof body tissues such as articular cartilage, ligaments and tendons.Target tissues subject to ablation and removal have many differentconfigurations and structures. These medical device probes and lasershave further disadvantages of being configured for simple ablationwithout regard to the contour and structure of the target tissue. Byuniversally applying RF energy to the site, non-target tissue may beaffected by collateral thermal effects.

[0008] For these reasons it would be desirable for an apparatus andmethod to selectively cut and ablate body tissue during a medicalprocedure such as arthroscopic surgery. The apparatus and method shouldbe configured and used for effective cutting, ablation and vaporizationof target tissue while giving the surgeon a precise and controlledsurface for scraping tissue from bone or sculpting tissue within thesurgical field for appropriate treatment and therapy. Such apparatus andmethods should also be applicable in a wide variety of medicalprocedures on a wide range of different bodily tissues. The apparatusshould also be simple and less expensive to manufacture while beingcompatible with conventional systems and procedures.

SUMMARY OF THE INVENTION

[0009] One embodiment of the invention is based on a surgical apparatus,comprising: an energy application tip including: a length of shaft; andan active electrode having a curved current density edge with at leastone convex surface.

[0010] Another embodiment of the invention is based on a method ofsurgically treating a mammal in need thereof, comprising: providing asurgical instrument including a length of shaft and an active electrodehaving a curved current density edge with at least one convex surface;and ablating a tissue surface with said surgical instrument.

[0011] Another embodiment of the invention is based on anelectrosurgical system for directing thermal energy to tissue isdisclosed which has a power supply and a probe. The probe is coupled tothe power supply by a cabling means and has a handle and a shaftincluding a distal end and a proximal end. The shaft has at least onelumen for an active electrode electrically coupled to the power supply,the active electrode being positioned on the distal end of the probe,the active electrode having an energy application surface; and a returnelectrode electrically coupled to the power supply.

[0012] These, and other, goals and embodiments of the invention will bebetter appreciated and understood when considered in conjunction withthe following description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a lateral view of internal structures within theglenohumeral joint.

[0014]FIG. 2 is a medial side view of the knee joint.

[0015]FIG. 3 is an anterior view of the knee joint with the patellaremoved.

[0016]FIG. 4 is a perspective view of a concave cutting tip of a RFprobe.

[0017]FIG. 5 is a perspective view of the concave cutting tip of FIG. 4inserted into the shaft portion of the RF probe.

[0018] FIGS. 6A-B are side views of the concave cutting tip of the RFprobe of FIG. 4.

[0019]FIG. 6C is an alternative embodiment of the concave cutting tip ofthe RF probe.

[0020] FIGS. 7-11 show different monopolar and bipolar arrangements ofthe electrodes on the concave cutting tip.

[0021] FIGS. 12A-C show an overview of a RF probe, operating cannula anda side, cross-sectional view of the shaft portion of the RF probe.

[0022]FIG. 13A illustrates an alternate embodiment of a probe withcutting tip.

[0023]FIG. 14A is a simplified, side view of the probe according to theinvention;

[0024] FIGS. 14B-14F show alternative tip configurations of the probe.

[0025] FIGS. 15A-C are isometric, top and cross-sectional views,respectively, showing one embodiment of an active electrode and anenergy application tip of the probe according to the invention.

[0026] FIGS. 15D-F are isometric, top and cross-sectional views,respectively, showing an alternate embodiment of the active electrode.

[0027] FIGS. 15G-I are isometric, top and cross-sectional views,respectively, showing an alternate embodiment of the active electrodeand distal tip of the probe.

[0028] FIGS. 16A-F are side and isometric, perspective views ofdifferent embodiments of the probe according to the invention.

[0029]FIG. 17A is a cross-sectional view of one of the distal energyapplication tips and active electrode of the probe according to theinvention.

[0030] FIGS. 17B-C are side views of different embodiments of the probe.

[0031]FIG. 18A is a cross-sectional view of an alternative embodiment ofthe distal energy application tip and active electrode of the probeaccording to the invention.

[0032]FIG. 18B is an isometric perspective view of the probe.

[0033] FIGS. 19A-B are side, cross-sectional views of an alternativeembodiment of the distal energy application tip and active electrode ofthe probe according to the invention.

[0034] FIGS. 20A-B are side, cross-sectional and isometric perspectiveviews, respectively, of the probe of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0035] The invention arose out of an observation that, during anarthroscopy procedure, the surgeon could not access and cut cleanly thecoracoacromial (CA) ligament shown in FIG. 1. This procedure is done inconjunction with a subacromial decompression, which makes a painfulshoulder easier to move. If the cutting probe slips, the joint capsulecould be damaged and even punctured, which would exacerbate an alreadypainful joint. Thus, a concave rounded tip was designed which wouldcenter and position ligaments and could even be used to lift theligament away from adjacent structures and avoid harm thereto.

[0036] This new style of tip has the advantage of being able tomechanically “gather” or constrain ligaments, tendons and other tissueinto its center. This reduces the natural tendency of current cuttingprobes to slide off ligaments and tendons. This helps save time in thatthe surgeon is not repeatedly trying to center or approximate the probetip on the target tissue.

[0037]FIG. 1 show s a lateral (side) view of a glenohumeral joint 100and in particular the Coracoacromial ligament 102, the Superiorglenohumeral ligament 104, the middle oienohumeral ligament 106, theSubscapularis Tendon 108 (joined to capsule), the Inferior Glenoheumeralligament 110, the Glenoid “cup” with cartilage 112, the Joint Capsule114, and the Bursa 116. The Joint Capsule 114 is comprised of 3glenohumeral ligaments and surrounding capsule. The Bursa 116 lubricatesand acts like a shock absorber, and is usually removed when an SAdecompression is performed. The area 118 is the area at whichimpingement usually occurs.

[0038]FIG. 2 shots s a medial (side) view of a patellofemoral or kneejoint 200, and in particular the Medial Collateral Ligament 202, thepatella 204, the Medial Lateral Retinaculum 206, an incision line 208for lateral release and the Patellar Ligament 210.

[0039]FIG. 3 illustrates an anterior view of the knee joint 200 with thepatella removed. The bones comprising the knee joint 200 are the femur240, the fibula 250 and the tibia 260. The joint is connected byligaments, in particular, the anterior cruciate ligament 200 and theposterior cruciate ligament 230. As the knee is flexed, the lateralcondyle of the femur 241 and the medial condyle of the femur 242articulate and pivot on the meniscal surfaces of the tibia, inparticular the lateral meniscus 231 and the medial meniscus 232,respectively. The meniscal surface comprises articular meniscalcartilage which acts as the shock absorber for the knee.

[0040] While coracoacromial surgery was the inspiration for thisinvention, use of this concave probe is not limited to a particularligament or tendon, or even to those soft tissues. The concave cuttingprobe is adapted to cut all types of tendons, ligaments and soft tissuesmore effectively than blunt or rounded tip probes. As another examplewhose anatomy is shown in FIG. 2, the lateral retinaculum 206 sometimesmust be severed in some types of patellar dislocation or malignment,when the patella is not properly tracking in the trochlear notch.Severing the lateral retinaculum is called lateral retinacular release.With this concave-tip probe, the surgeon is able to position theligament and sever it cleanly.

[0041] The probe of the invention may also be used in the knee jointduring a notchplasty procedure for anterior cruciate ligament repair.The probe configuration of the invention, in particular the energyapplication tip configuration is used to remove and scrape the condylarsurfaces of the femur to increase the interchondylar notch to free theanterior cruciate ligament from impingement. The anterior cruciateligament may also be cut at point 221 and removed using the probe and apatellar tendon graft may be performed.

[0042] Turning note to the probe itself, FIG. 4 shows a concave edge 308on a distal tip 304 of an RF probe head 300. This concave edge isdesigned to constrain tissue, tendons and ligaments. The concave curvehas lateral edges 306 which are rounded, so that the probe does not“snag” on unwanted tissue as the surgeons maneuvers the probe intoposition. The cylindrical portion 302 of the distal tip 304 fits insideprobe sheath 410, as shown in FIG. 5. The distal tip may have a varietyof configurations, as shown in FIGS. 4-11. FIG. 5 shows probe 400 havinga concave edge with less prominently rounded lateral edges. FIGS. 5-7show a distal tip which is angled with respect to the sheath 410. Thisembodiment offers the advantage of helping the surgeon get aroundcorners and ablate in narrow or confined spaces.

[0043]FIG. 6A shows an angled probe 500 consisting of a cylindricalportion 502 with a distal tip 504 having a concave edge 508 and lateraledges 506. FIG. 6B shows a side view of angled probe 500.

[0044]FIG. 6C shows an angled probe 600 with a specialized surface (notheated) which imparts a third function to the probe, namely scrapingtissue. Probe 600 is comprised of a cylindrical portion 602, and adistal tip 604 which has a concave edge 608 and lateral edges 606. Thesurface of the flat portion of distal tip 604 contains rasps 616 whichcan be used for scraping tissue.

[0045] For cutting tissue, the distal tip has a first electrode and asecond electrode located on lateral edges 606. The first and secondelectrodes can be operated in bipolar or monopolar mode. Bipolar ispreferred and examples of “Taser” type electrodes are shown in FIGS. 7and 8.

[0046]FIG. 7 shots s a distal tip 700 having a three-pole, bipolararrangement where, in addition to two side positive electrodes 702 and706, there is a central negative electrode 704. FIG. 8 shows a distaltip 800 wherein two electrodes 802 and 806 are positioned in two smallsites on the lateral edges of the concave curve. In this particularembodiment, electrode 802 is positive and electrode 806 is negative

[0047] FIGS. 9-11 show exemplary monopolar arrangements. In FIG. 9, asingle monopolar positive electrode 902 occupies a wide portion of theconcave curve of distal tip 900. A return path 904 is provided and isattached to the patient's body to complete the circuit. In FIG. 10,there is one small active electrode 1006 located centrally on distal tip1000. In FIG. 11 there are two active electrodes 1102 and 1106 inlateral positions on distal tip 1100. Suffice it to say that quite avariation in electrode design is contemplated for this concave curve.

[0048] To maintain the appropriate temperature for cutting tissue, thedistal tip of the probe may also be equipped with a thermocouple, butsuch a thermocouple is optional in the concave-tipped probe.

[0049]FIG. 12 illustrates a simplified view of the RF probe of theinvention. FIG. 12A is an illustration of a conventional cannulautilized in one embodiment of the invention. Cannula 1202 consists of aguide 1224 with an opening 1226 at its distal end. Cannula 1202 isattached at its proximal end to introducer 1222. Instrument port 1228 islocated at the proximal end for the introduction of the surgical probe.Cannula 1202 man also have an extension 1232 with a fluid port 1234. Asillustrated in FIG. 12B, surgical instrument 1200 consists of a handle1212 to which is attached a power cord 1210, a probe shaft 1214 and aprobe tip 1216. During introduction into the body, a blunt insert orobturator (not shown) is inserted through instrument port 1228. Cannula1202 is inserted into the surgical site on the patient functioning as atrocar. Surgical instrument 1200 is then inserted into cannula 1202through instrument portal 1228 so that the tip 1216 protrudes from theopening 1226 in cannula 1202.

[0050]FIG. 12C illustrates a side, cross-section of the probe shaft1214. Probe handle 1212 is connected to shaft tubing 1242. Shaft tubinginsulator 1241 covers the shaft tubing. The shaft tubing insulator 1421may be any biocompatible material such as Teflon or any other suitablematerial such as nylon shrink tubing. Power wire 1260 is connected to apower supply (not shown) in the proximal portion of the probe and probehandle 1212. Power insulator 1267 covers and insulates power wire 1260.The power insulator 1267 material is preferably a tubing such as Teflonor polyimide but may also include any other insulator material whichwould be known by a person skilled in the art such as a coating. Powerwire 1260 connects the power supply to an active electrode (not shown)on the distal energy application tip 1250. The power wire may bestainless steel, titanium, tugsten, copper or any other compatible andsuitable conductor. A return wire 1261 connects a return electrode (notshown in FIG. 12) to the power supply. The energy application tip 1250has an energy application surface 1255. The energy application surface1255 is configured to have a variety of configurations such as concave,convex or concavo-convex for the delivery of thermal energy to the softtissue site. Probe shaft tubing, 1242 may also have a bent portion 1251which may be configured for easier access to narrow or confined jointspaces.

[0051] FIGS. 13A-B show an enlarged view of one embodiment of the tip1510 of an electrosurgical instrument wherein two opposing arcuatesegments 1504A and 1504B are compressed to form a probe tip 1216A at thedistal end of probe 1214A. In such an embodiment, swagging is used tocompress the tip of the probe. Swagging forms a chisel 1514 that can beused in the surgical instrument of FIGS. 12 and 13 for RF ablation oftissue. Grinding applications can be added to the tip to provide formechanical tissue ablation in addition to energy ablation. The core 1502of probe 1214A can be either hollow or solid. This particular embodimentis illustrated as having an annular probe. Probe 1214A is coated in aninsulating material which terminates prior to the tip 1510, leavingchisel 1514 exposed. The surgical probe illustrated in FIGS. 13A-Bprovides various improvements over the prior art in allowing for precisehemostatic cutting and ablation of soft tissue in one convenientinstrument which can be described as a chisel. The malleable probe tipscan be configured as straight, angled or curved, for example, whichprovides for optimal access to specific anatomy and pathology. Uniquetip designs improve tactile feedback for optimal control and access, andprovide for improved tissue visualization with greatly reduced bubblingor charring.

[0052] Another embodiment of surgical probe of the invention isillustrated in FIGS. 14A-F. FIG. 14A illustrates a simplified side viewof the surgical probe for the delivery of thermal energy to a tissuesite. FIGS. 14B-F shots Various alternative embodiments of the energyapplication tip. The configuration of the probe shaft allows the surgeonto have better access and more selective control while in the operatingenvironment. For example. FIG. 14D is particularly suitable for use inan arthroscopic acromioplasty wherein the coracoacromial ligament is cutand associated tendons are removed. The right angle of the energyapplication tip allows the surgeon to scrape target tissue from theunderside of the acromion. The various other configurations andgeometries of the energy application tip as shown in FIGS. 14B-14F allowthe surgeon to operate in a variety of arthroscopic procedures to accessvarious joint geometries within the body. The probe may also bemalleable to allow the surgeon to adjust the distal tip for anindividual and procedure.

[0053] FIGS. 15A-15C illustrate one embodiment of the distal energyapplication tip of the probe according to the invention. The energyapplication surface comprises an active electrode 1520 in the form of a“cross” or “crossfire” for the delivery of electrical energy to a tissuesite during a surgical procedure. The electrical characteristics of thiscross-shape design and configuration of the active electrode 1520condenses and concentrates the electrical current density at definedcurrent density edges 1529 along cross-shape on the distal tip. Thereturn electrode 1523 is also located near the distal energy applicationtip such that a unipolar arrangement for RF energy delivery isdescribed. An insulating collar 1525 separates active electrode 1520from return electrode 1523.

[0054] Turning to FIG. 15C, power wire 1560 delivers energy from thepower source to the active electrode 1520. Power insulator 1567insulates the power ire inside the probe and between the shaft tubingand electrodes. Insulating collar 1525 insulates the active electrode1520 from the return electrode 1523 which may be formed from a portionof the shaft tubing or a separate electrode on the distal tip.Alternatively, a separate return electrode structure may be used whichis separate from the distal energy application tip. The current travelsbetween the active electrode and the return electrode through theirrigation solution or through the tissue.

[0055] For example, it will be appreciated by one skilled in the artthat in an alternating current system, the generated and delivered highfrequency RF energy (greater than 300 kHz) will alternate between theactive electrode 1520 and the return electrode 1523. By using a largersurface area return electrode in proportion to the active electrode, theRF energy is diffuse in the area of the return electrode. When theenergy is applied to the distal energy application tip, heat isgenerated at the sharp edges 1529 of active electrode 1520 activatingthe entire electrode surface while heat is minimized at the returnelectrode 1523 through diffusion. Because electrical current iscondensed and concentrated on a smaller area, heat is generated at adirected and desired area such as the target tissue in contact with theenergy application tip. This allows the surgeon to cut and ablate thetarget tissue in a more efficient manner when the tissue causes anincrease in impedance between the two electrodes. The crossconfiguration and edges 1529 also provides a specific mechanical surfacefor a physical scraping function of the active electrode. The tissue andstandard irrigation in the surgical joint complete the circuit betweenthe two electrodes and the tissue is mechanically and thermally cut andablated allowing the surgeon to vaporize the target tissue such as whenremoving a soft cartilage tissue from bone.

[0056] Thus, the distal energy application tip of the invention may befurther described as “unipolar” or “sesquipolar” whereby one electrodehas a different electrical potential than the other electrode. In a truebipolar system, each electrode would have equal potentials and equaleffects when electrical energy is applied to the active electrodes. Inthe invention, the active electrode generates heat by condensing the RFenergy at the sharp edges causing cutting, ablation and vaporizationwhile the return electrode generates little heat. It will also beappreciated that due to the high frequency current, these distal energyapplication tips and active electrode designs may be used inconventional monopolar surgical systems where the return electrode islocated on the patient's body.

[0057] FIGS. 15D-F illustrate another embodiment of the distal energyapplication tip 1500 of the invention wherein the active electrode 1530is constructed in a “cloverleaf” configuration. As described in FIG.15A, the RF energy is condensed and directed through current densityedges 1529 towards the target tissue. Active electrode 1530 has themechanical advantage of a greater scraping ability by providing a sharpcurrent density edge 1539. Power wire 1560 is covered with powerinsulator 1567 and delivers energy to the active electrode 1530. It willbe appreciated that all current density edges will have the same currentpotential whereby the potential for an ablation and vaporization effectis uniform at all tissue contact points.

[0058] FIGS. 15G-I illustrate another embodiment of the distal energyapplication tip 1500 of the invention wherein the active electrode 1540is an “ashtray” configuration. As described in FIG. 15A, the RF energyis condensed and directed through current density edges 1549 towards thetarget tissue. Active electrode 1540 has a further mechanical advantageof a greater scraping ability by providing a sharp current density edge15539 while having a thermal energy effect at the current density edges1539. Power wire 1560 is covered with power insulator 1567 and deliversenergy to the active electrode 1540. It will be appreciated that allcurrent density edges will have the same current potential whereby thepotential for an ablation and vaporization effect is uniform at alltissue contact points. As the RF power is delivered to the activeelectrode, the target tissue in contact with the surface of the currentdensity edges 1539 is uniformly cut and ablated for removal from thejoint. FIG. 15I also shows the power wire 1560 alternatively coupled tothe distal tip 1540 by means of an intermediate couple wire 1580.

[0059] It will also be appreciated that the active electrode can bebrazed, crimped soldered, welded or mechanically attached by means of aspring clip to the power wire. One alternative attachment means includesproviding an active electrode with a hole. When the electrode is heated,the hole expands and the power wire is inserted into the hole. As theelectrode tip cools, the diameter of the hole will decrease therebyeffectively crimping the electrode tip to the power wire. Further, theactive electrode may consist of titanium, tungsten and their alloys orstainless steel and the power wire may consist of stainless steel in avariety of tensile strengths, titanium, copper or any suitable alloysthereof. The active electrode tip may also be machined, stamped, castinto shape or metal injection molded to form the desired configurationwith current density edges.

[0060]FIG. 16A-B show side and perspective views of ashtray electrodeconfigured for sculpting soft tissue attached to bone or any other softtissue within the body. The distal energy application tip is arcuatesuch that the shaft tubing is bent between 0 and 90 degrees. The shaft1624 is preferably 30 degrees to provide an angle for sculpting the softtissue by ablation. In this embodiment, the return electrode 1623 isformed from the distal portion of the shaft tubing and electricallyconnected to the power supply to act as the return in a unipolarconfiguration.

[0061] As shown in FIG. 16A, the current density edge 1629 has cutoutsor gaps whereby the RF energy is focused primarily on the external edgesof the active electrode thereby heating up specific areas of targettissue adjacent to the probe. As the power level of the RF energyincreases, the target tissue is cut and ablated in a consistent patternto vaporize the tissue along the current density edge 1629 as thesurgeon manipulates the probe within the surgical field.

[0062] In FIGS. 16C-D, the active electrode is shown in an alternativeembodiment having a dome structure with a convex surface for ablationand vaporization. Active electrode 1630 has a simple base with a domedefining a broad surface current density edge. As the RF power isapplied to the active electrode, the target tissue is sculpted in asmooth and consistent ablation. Surgical procedures using a smoothingablation and vaporization include meniscal repair and capsulotomy whereextra cartilage and ligament material can irritate the joint if it isnot cut out and removed by ablation and vaporization.

[0063] FIGS. 16E-F illustrate an alternative embodiment wherein the domeof FIGS. 16C-D has a dimple within the convex dome structure. As thevaporization occurs, constant bubble streams with small bubblesresulting from cellular destruction and dessication obscure theoperating field and arthroscope where the surgeon views the arthoscopicprocedure. The dimple allows the bubbles to collect and form a largerbubble which is then released from the void defined by the dimple at aninfrequent rate. This allows the surgeon to have an unobstructed view ofthe tip while still allowing the energy application tip 1600 to deliverRF energy to the active electrode so as to effect ablation. Currentdensity edges 1649 provide for a condensation and concentration of RFenergy along the edges of the active electrode 1640 to heat up thetarget tissue in contact with the edges thereby causing ablation andvaporization.

[0064] Turning to FIG. 17A, the distal energy application tip 1700 isillustrated in a detailed cross-section. The active electrode 1710 isprovided in an ashtray configuration. The current density edges 1719 arelocated on a distal portion of the active electrode. Gap portions 1712allow the RF energy to be condensed and concentrated at the currentdensity edges 1719. The active electrode 1710 is inserted into aninsulating collar 1715 for attachment to the distal end of the shafttubing 1742.

[0065] In a unipolar setting the return electrode 1742 is located nearthe end of the distal tip of the shaft tubing 1742. Alternatively, thereturn electrode 1742 may be formed from a portion of the shaft tubing1742 thereby allowing for a simpler construction. Shaft insulation 1741insulates the shaft in conjunction with insulating collar 1715. Powerwire 1760 delivers the RF energy to the active electrode from the powersupply and is located within the shaft tubing lumen 1780. Return wire1761 is coupled to return electrode 1713 to function as a return to thepower supply.

[0066] FIGS. 17B-C show alternative embodiments of the shaft with theashtray active electrode. FIG. 17B illustrates the ashtray activeelectrode being configured for sculpting the target tissue wherein thedistal end of the shaft 1734 is bent to a right angle. The activeelectrode 1720 with current density edges 1729 is located on the distalportion of shaft 1724. The return electrode 1723 is separated fromactive electrode 1720 by insulating collar 1725.

[0067]FIG. 17C illustrates the ashtray active electrode being configuredfor scraping target tissue from bone. The active electrode 1730 withcurrent density edges 1739 is located on the distal portion of shaft1734. The return electrode 1733 is separated from active electrode 1730by insulating collar 1735.

[0068]FIG. 18A-B shows a detailed cross-section and perspective view ofthe distal energy application tip 1800 with a cross-configured activeelectrode 1810. In an exemplary embodiment the active electrode 1810 isinsulated from return electrode 1813. The return electrode 1813 may alsobe formed from a portion of the shaft tubing 1842. Power wire 1860located within the shaft tubing lumen 1880 delivers RF energy to theactive electrode 1810. The current density edges 1819 provide a surfacefor the current to condense causing ablation and vaporization of thetarget tissue. Shaft insulation 1841 protects and insulates shaft tubing1842.

[0069]FIG. 19A-B illustrate another embodiment of the active electrodewherein the distal energy application tip 1900 is configured forgrating. In this embodiment, active electrode 1910 is a ring electrodewith a continuous current density edge 1919. In this configuration, theactive electrode defines a lumen 1985 with insulator block 1962 formingthe back wall portion of the lumen. Insulator collar 1915 insulates theactive electrode 1910 from the return electrode 1913. Insulator collar1915 is attached to the distal portion of shaft tubing, 1942. The shaft1914 is covered in shaft insulator 1941. In FIG. 19B, the returnelectrode 1903 is located within active electrode lumen 1985. In thisconfiguration, a boiling chamber is created wherein any additionalmaterial that is grated and scraped into the lumen and not fully ablatedor vaporized will increase the impedance between the active and returnelectrodes to cause further vaporization. As the ring electrode isplaced against target tissue and RF energy is delivered through powerwire 1960, ablation and vaporization occurs at the current density edge1919.

[0070]FIG. 20A-B illustrate an alternative embodiment of the distalenergy application tip 2000 wherein the active electrode 2010 has acomplex teeth structure for mechanical gratings during ablation andvaporization. In this embodiment, the active electrode 2010 is formedfrom by machining or cutting curves or teeth into the ring electrode. Inthis configuration, the current density edges 2019 provide a tooth-likegrater to mechanically scrape the target tissue. RF power is deliveredby power wire 2060 through insulating block 2062. The active electrode2010 is insulated from return electrode 2013 by insulating collar 2015.The insulating collar 2015 is located on the distal portion of shafttubing 2042 which is insulated by shaft insulator 2041. Return wire 2061is coupled to return electrode 2013 to function as a return to ground atthe power supply. While shaft 2014 is shown as linear, it may bemalleable or pre-bent to allow for appropriate access and control withinthe surgical environment.

EXAMPLE

[0071] Lateral retinacular release as mentioned above can beaccomplished with the use of the concave-tipped RF probe as shown inFIG. 4. First, the knee joint is distended with a clear fluid, usuallysaline. Initial distention can be done using a large syringe full ofsaline which is injected into the joint space. Distention forces thebones of the joint apart creating room to introduce instrumentationwithout damaging the cartilage.

[0072] Once the instrumentation has been inserted into the joint space,the irrigation tubing and cannulas are positioned and hooked up toprovide continual fluid exchange during the procedure. The most commonsystems are gravity flow or the use of an arthroscopic pump. By hangingbags of irrigation fluid on an IV pole and raising them 3-4 feet abovethe operative site, flow to the joint can be accomplished. Elevation ofthe supply bag is enough to create pressure to distend and irrigate thejoint. The fluid enters the joint through the scope sheath and exitsthrough a cannula placed in the superior lateral portal, or the reverse,through the cannula and out through the scope sheath. The setup is amatter of physician preference. The key to the proper function of eithersystem is that the inflow volume must be larger than the outflow volume.This restriction in the outflow is what creates the back flow thatdistends the joint.

[0073] With an arthroscopic pump, the bags do not need to be raised onan IV pole. The factors controlling distention of the joint arecontrolled automatically by the pump. The pump monitors the fluidpressure in the joint space using a pressure sensing cannula andautomatically increases or decreases fluid flow as needed to provideoptimum viewing. As with the gravity flow system, fluid enters the jointcavity through the scope sheath or the cannula in the superior lateralportal. Such an arthroscopic procedure requires the creation of two tofive portals (entry ways) into the joint capsule. To create a portal,the surgeon usually begins by making a small stab wound with a scalpel(e.g.. No. 11 or 15 blade) at the site of the portal. Next, the wound isenlarged and extended with a trocar encased in a sleeve (cannula)through muscle tissue to the synovial membrane. The trocar is removed,leaving the cannula in place. Then, the surgeon uses a blunt obturator(to avoid damage to menisci and articular cartilage) to puncture throughthe synovium into the joint cavity. The obturator is removed and thecannula left in place. The cannula can be used to insert an arthroscopeor for the inflow and outflows of water. If the surgeon elects to insertinstruments percutaneously, the sleeve is removed. For lateralretinacular release, the surgeon frequently uses three portals, one forthe arthroscope, one for the instrument and one for the drain.Additional portals may be created for the surgeon to access other areasof the knee (i.e., to tighten the medial retinaculum) during theprocedure. Frequently, a superolateral (above and to the side of thepatella) approach is used for the irrigation cannula. For thearthroscope and concave probe, anteromedial and anterolateral approachesoften are chosen, because they are relatively safe (minimal potentialtissue damage) and most surgeons have more experience with them. Oncethe arthroscope is viewed, the surgeon may use the concave-tipped probe(without power) to advance to the site of the lateral retinaculum.Having located the lateral retinaculum, the surgeon activates the RFprobe and cuts entirely through the ligament.

[0074] The foregoing description of a preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in this art. Itis intended that the scope of the invention be defined by the followingclaims and their equivalents.

[0075] All publications and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated to be incorporated by reference.

[0076] While the invention has been described with respect to itspreferred embodiments, it will be appreciated that other alternativeembodiments may be included. For example, with respect to all of theexplicitly disclosed embodiments, as well as all other embodiments ofthe invention, monopolar implementation may be achieved by replacing thereturn electrode on the probe with a separate return electrode, oralternatively, simply providing an additional electrode as a returnelectrode on the body of a patient electrically utilizing the returnelectrode on the probe. These and various other modifications can bemade to the disclosed embodiment without departing from the subject ofthe invention.

What is claimed is:
 1. A surgical apparatus, comprising: an energyapplication tip including: a length of shaft: and an active electrodehaving a curved current density edge with at least one convex surface.2. The surgical apparatus of claim 1, wherein said length of shaftincludes a substantially linear section near the tip.
 3. The surgicalapparatus of claim 2, wherein said curved current density edge defines acrossfire pattern.
 4. The surgical apparatus of claim 2, wherein saidcurved current density edge defines a cloverleaf pattern.
 5. Thesurgical apparatus of claim 2, wherein said curved current density edgedefines an ashtray pattern.
 6. The surgical apparatus of claim 2,wherein said curved current density edge defines a dome pattern.
 7. Thesurgical apparatus of claim 2, wherein said curved current density edgedefines a dome with dimple pattern.
 8. The surgical apparatus of claim2, further comprising an insulating collar coupled to a distal end ofsaid shaft.
 9. The surgical apparatus of claim 8, wherein said length ofshaft includes a return electrode that defines said distal end of saidlength of shaft.
 10. The surgical apparatus of claim 9, furthercomprising a return wire coupled to said return electrode.
 11. Thesurgical apparatus of claim 1, wherein said length of shaft includes acurved section having a substantially constant radius of curvature. 12.The surgical apparatus of claim 11, wherein said curved current densityedge defines a crossfire pattern.
 13. The surgical apparatus of claim11, wherein said curved current density edge defines a cloverleafpattern.
 14. The surgical apparatus of claim 11, wherein said curvedcurrent density edge defines an ashtray pattern.
 15. The surgicalapparatus of claim 11, wherein said curved current density edge definesa dome pattern.
 16. The surgical apparatus of claim 11, wherein saidcurved current density edge defines a dome at with dimple pattern. 17.The surgical apparatus of claim 11, further comprising an insulatingcollar coupled to a distal end of said shaft.
 18. The surgical apparatusof claim 17, wherein said length of shaft includes a return electrodethat defines said distal end of said length of shaft.
 19. The surgicalapparatus of claim 18, further comprising a return wire coupled to saidreturn electrode.
 20. The surgical apparatus of claim 1, wherein saidlength of shaft includes an arcuate section.
 21. The surgical apparatusof claim 20, wherein said curved current density edge defines acrossfire pattern.
 22. The surgical apparatus of claim 20, wherein saidcurved current density edge defines a cloverleaf pattern.
 23. Thesurgical apparatus of claim 20, wherein said curved current density edgedefines an ashtray pattern.
 24. The surgical apparatus of claim 20,wherein said curved current density edge defines a dome pattern.
 25. Thesurgical apparatus of claim 20, wherein said curved current density edgedefines a dome at with dimple pattern.
 26. The surgical apparatus ofclaim 20, further comprising an insulating collar coupled to a distalend of said shaft.
 27. The surgical apparatus of claim 26, wherein saidlength of shaft includes a return electrode that defines said distal endof said length of shaft.
 28. The surgical apparatus of claim 27, furthercomprising a return wire coupled to said return electrode.
 29. Thesurgical apparatus of claim 1, wherein said length of shaft includes acurved section having a right angle.
 30. The surgical apparatus of claim29, wherein said curved current density edge defines a crossfirepattern.
 31. The surgical apparatus of claim 29, wherein said curvedcurrent density edge defines a cloverleaf pattern.
 32. The surgicalapparatus of claim 29, wherein said curved current density edge definesan ashtray pattern.
 33. The surgical apparatus of claim 29, wherein saidcurved current density edge defines a dome pattern.
 34. The surgicalapparatus of claim 29, wherein said curved current density edge definesa dome with dimple pattern.
 35. The surgical apparatus of claim 29,further comprising an insulating collar coupled to a distal end of saidshaft.
 36. The surgical apparatus of claim 35, wherein said length ofshaft includes a return electrode that defines said distal end of saidlength of shaft.
 37. The surgical apparatus of claim 36, furthercomprising a return wire coupled to said return electrode.
 38. A methodof surgically treating a mammal in need thereof, comprising: providing asurgical instrument including a length of shaft and an active electrodehaving a curved current density edge with at least one convex surface;and ablating a tissue surface with said surgical instrument.
 39. Themethod of claim 38, wherein ablating said tissue surface includesscraping said tissue surface.
 40. The method of claim 38, whereinablating said tissue surface includes sculpting said tissue surface. 41.A surgical apparatus for ablating tissue, comprising: a energyapplication tip including: a length of shaft; and a means for defining acurved current density edge with at least one concave surface
 42. Thesurgical apparatus of claim 41, wherein said length of shaft includes asubstantially linear section.
 43. The surgical apparatus of claim 41,wherein said length of shaft includes a curved section having asubstantially constant radius of curvature.
 44. The surgical apparatusof claim 41, wherein said length of shaft includes a curved sectionhaving an arcuate section.
 45. The surgical apparatus of claim 41,wherein said length of shaft includes a curved section having rightangle.
 46. A surgical apparatus, comprising: an energy application tipincluding: a length of shaft tubing; and an active electrode having acurved current density edge with at least one convex surface.
 47. Thesurgical apparatus of claim 46, wherein said active electrode isadjacent an inner surface of said length of shaft tubing.
 48. Thesurgical apparatus of claim 47, further comprising a return electrodeadjacent an outer surface of said length of shaft tubing.
 49. Thesurgical apparatus of claim 46, wherein said active electrode isadjacent an outer surface of said length of shaft tubing.
 50. Thesurgical apparatus of claim 49, further comprising a return electrodeadjacent an outer surface of said length of shaft tubing.
 51. Thesurgical apparatus of claim 46, wherein said active electrode defines aplurality of longitudinal recesses that are substantially parallel to anaxis defined by said length of shaft tubing.
 52. The surgical apparatusof claim 46, wherein said length of shaft tubing includes asubstantially linear section.
 53. The surgical apparatus of claim 46,wherein said length of shaft tubing includes a curved section having asubstantially constant radius of curvature.
 54. The surgical apparatusof claim 46, wherein said length of shaft tubing includes a curvedsection having a right angle.
 55. A surgical system for directingthermal energy to tissue, comprising: a power supply; a probe coupled tothe power supply, by cabling means, the probe having a handle and ashaft including a proximal end and a distal end, the shaft having atleast one lumen; an active electrode electrically coupled to the powersupply, the active electrode being positioned on the distal end of theprobe, the active electrode having an energy application surface; and areturn electrode electrically coupled to the power supply.
 56. Thesurgical system according to claim 55, wherein the distal end includesan insulating base member.
 57. The surgical system according to claim55, wherein the active electrode is configured for vaporizing a tissuestructure.
 58. The surgical system according to claim 55, wherein theactive electrode is configured for sculpting a tissue structure.
 59. AnRF probe comprising: a handle: a shaft coupled to the handle, the shafthaving a proximal end and a distal tip; an active electrode positionedat or near the distal tip, the active electrode having a energyapplication surface; and a return electrode.
 60. The RF probe accordingto claim 59, wherein the return electrode is formed from a portion ofthe shaft.
 61. The RF probe according to claim 59, wherein the returnelectrode is a grounding pad.
 62. A method for vaporizing tissuestructures within a body comprising: providing an RF probe with a distaltip with complex curves; approximating the RF probe to the tissuestructures to be vaporized; and applying RF energy through the complexcurves, thereby vaporizing the tissue structures.
 63. The methodaccording to claim 62, wherein the distal tip is concavo-convex.